checkpoint(new_editor): native d3d12 ui path

Key node 1: move main-window UI presentation onto the D3D12 render loop with native UI renderer, text system, and texture host.

Key node 2: wire frame timing/FPS display, window runtime, swapchain presentation, and native screenshot capture around the new path.

Key node 3: carry editor shell/workspace/viewport/panel interaction updates needed by the new renderer and detached window flow.

Key node 4: pump async resource loads and scene bridge follow-up needed for scene content visibility in new_editor.

new_editor/app/Rendering/D3D12/D3D12WindowSwapChainPresenter.cpp

@@ -240,15 +240,15 @@ bool D3D12WindowSwapChainPresenter::RecreateBackBufferViews() {
     return true;
 }
 
-bool D3D12WindowSwapChainPresenter::PreparePresentSurface(
+bool D3D12WindowSwapChainPresenter::PrepareCurrentBackBufferForRender(
     const ::XCEngine::Rendering::RenderContext& renderContext) {
     if (!renderContext.IsValid() || renderContext.commandList == nullptr) {
-        m_lastError = "PreparePresentSurface requires a valid render context.";
+        m_lastError = "PrepareCurrentBackBufferForRender requires a valid render context.";
         return false;
     }
 
     if (m_swapChain == nullptr) {
-        m_lastError = "PreparePresentSurface requires an initialized swap chain.";
+        m_lastError = "PrepareCurrentBackBufferForRender requires an initialized swap chain.";
         return false;
     }
 
@@ -256,7 +256,7 @@ bool D3D12WindowSwapChainPresenter::PreparePresentSurface(
     if (backBufferIndex >= m_backBufferViews.size() ||
         m_backBufferViews[backBufferIndex] == nullptr) {
         std::ostringstream error = {};
-        error << "PreparePresentSurface could not find the current swap chain RTV. index="
+        error << "PrepareCurrentBackBufferForRender could not find the current swap chain RTV. index="
               << backBufferIndex
               << " rtvCount="
               << m_backBufferViews.size();
@@ -272,6 +272,38 @@ bool D3D12WindowSwapChainPresenter::PreparePresentSurface(
     return true;
 }
 
+bool D3D12WindowSwapChainPresenter::FinalizeCurrentBackBufferForPresent(
+    const ::XCEngine::Rendering::RenderContext& renderContext) {
+    if (!renderContext.IsValid() || renderContext.commandList == nullptr) {
+        m_lastError = "FinalizeCurrentBackBufferForPresent requires a valid render context.";
+        return false;
+    }
+
+    if (m_swapChain == nullptr) {
+        m_lastError = "FinalizeCurrentBackBufferForPresent requires an initialized swap chain.";
+        return false;
+    }
+
+    const std::uint32_t backBufferIndex = m_swapChain->GetCurrentBackBufferIndex();
+    if (backBufferIndex >= m_backBufferViews.size() ||
+        m_backBufferViews[backBufferIndex] == nullptr) {
+        std::ostringstream error = {};
+        error << "FinalizeCurrentBackBufferForPresent could not find the current swap chain RTV. index="
+              << backBufferIndex
+              << " rtvCount="
+              << m_backBufferViews.size();
+        m_lastError = error.str();
+        return false;
+    }
+
+    renderContext.commandList->TransitionBarrier(
+        m_backBufferViews[backBufferIndex],
+        ::XCEngine::RHI::ResourceStates::RenderTarget,
+        ::XCEngine::RHI::ResourceStates::Present);
+    m_lastError.clear();
+    return true;
+}
+
 bool D3D12WindowSwapChainPresenter::PresentFrame() {
     if (m_swapChain == nullptr) {
         m_lastError = "PresentFrame requires an initialized swap chain.";